Magnet with vibratable armature



Nov. 6, 1962 J. J. RONCI 62,

MAGNET WITH VIBRATABLE ARMATURE Filed March 20, 1959 Fl G.

/2 Fl G. 4

FIG. 2

INVENTOR. JOHN J. RONCI BY ATTO R N EYS United States Patent Office 3,062,926 Patented Nov. 6, 1952 3,062,926 MAGNET WITH VIBRATABLE ARMATURE John J. Ronci, 35 Monroe St., Norwood, Mass. Filed Mar. 20, 1959, Ser. No. 800,744 4 Claims. (Cl. 179-115) This invention relates to a way of mounting an armature in a magnetic field which leaves the armature free to vibrate in response to variations in the field. One practical use of the invention is had by connecting the armature to the cone of a loud-speaker so that the vibrations of the armature result in the propagation of sound waves from the cone, but the usefulness of the invention is not limited to its use in connection with a loud-speaker.

As described hereinafter in more detail, the invention is embodied in an armature which is mounted between the poles of a horseshoe magnet or its equivalent in the area of densest magnetic flux, the armature being freely movable in a direction perpendicular to the direction of the line of densest flux but being restrained from moving into contact with either arm of the magnet itself.

FIGURE 1 is a diagrammatic sectional view of a loud-speaker in which an embodiment of the invention is included;

FIGURE 2 is a plan view of the magnet, armature and part of the cone shown in FIGURE 1;

FIGURE 3 is a section on the line 33 of FIGURE 1; and

FIGURE 4 is a fragmentary elevational view of a modified form of the invention.

The apparatus illustrated in FIGURE 1 comprises a horseshoe magnet mounted on a base 12, each of the arms of the magnet having a coil 14 of wire thereon, these coils being connected in the customary manner to a source (not shown) of oscillating current of audio frequency. Between the arms of the magnet is mounted an armature 16 which is preferably in the form of a thin plate of ferro-magnetic material such as soft iron. As indicated in FIGURE 2, this plate has a width slightly less than the distance between the end portions of the arms of the magnet 10. The armature is supported in line with the poles of the magnet so that it lies in the area of maximum density of flux in the magnetic field of the magnet 10. The armature 16 is supported by a hinge 20 on brackets 22 which are mounted within the casing 24. The hinge is preferably supplied with needle hearings or other anti-friction bearings so that the armature is freely swingable about the axis of the hinge and the portion between the poles of the magnet can move in a direction perpendicular to the plane of the armature itself, that is, in a direction parallel to the arms of the magnet 10. The side edges of the armature 16 are arranged to be as close as possible to the respective arms of the magnet but to be kept from physical contact therewith by the hinge 20. Oscillations of the current flowing through the coils 14 result in corresponding variations in the magnetic field in which the armature 16 is located. This produces vibratory rocking movements of the armature about the axis of the hinge 20 which can be put to any suitable use. For example, as illustrated in FIGURES 1 and 2, the armature 16 may be connected by a rigid bolt 26 to the cone of a loud speaker supported by the customary compliance 30. The vibrations of the armature 16 which are transmitted through the bolt 26 result in the emission of corresponding sound waves from the cone 28.

The modified form of the invention illustrated in FIG- URE 4 is like that hereinbefore described except that the armature 30 is a plate or strip of ferro-magnetic metal which is long enough and thin enough to be freely flexible so that while one end thereof is fixed to a block 32, the free end portion of the strip which is located between the poles of the magnet 10 can move freely in a direction perpendicular to its plane in response to variations in the current passing through the coils 14.

The use of the vibrating armature to transmit vibrations to the cone of a loud speaker unit is but one of the possible uses of the apparatus for converting variations in electric current to corresponding mechanical vibrations.

I claim:

1. In combination with a magnet of the horseshoe type having two spaced arms with magnetic poles therein, an armature consisting of a thin plate of ferro-magnetic material between said arms in the area of maximum density of magnetic flux, the plane of said plate being perpendicular to the plane defined by the arms of said magnet and parallel to the line from one magnetic pole to the other, and means supporting said armature with freedom to vibrate in a. direction perpendicular to its plane, said supporting means maintaining said armature out of physical contact with said magnet.

2. In combination with a magnet of the horseshoe type having two spaced magnetic poles, an armature comprising a thin plate of ferro-magnetic material in the area of magnetic flux of maximum density between said poles, the plane of said plate being perpendicular to the plane defined by the arms of said magnet and parallel to the line from one magnetic pole to the other, hinge means supporting said armature for free vibrating movement in a direction perpendicular to the plane of the armature but out of contact with said magnet, and a wire coil encircling a portion of said magnet to produce small variations in said magnetic flux in response to varying electric currents therein.

3. In combination with a horseshoe magnet having parallel arms, an armature comprising a plate of ferromagnetic material having a width slightly less than the distance between said arms, hinge means supporting said armature in the area of magnetic flux of maximum density between said arms and in a plane perpendicular to said arms and to the common plane of said arms, said hinge means being arranged to permit free vibration of said plate in a direction perpendicular to the plane thereof, and coils of wire around said arms to vary the magnetic field of the magnet in response to varying currents in said wire.

4. Apparatus as described in claim 3, in combination with a loud-speaker cone and a rigid element connecting said armature to the apex of the cone.

References Cited in the file of this patent UNITED STATES PATENTS 220,839 Hubbard Oct. 21, 1879 1,788,557 Aull et al. Jan. 13, 1931 1,967,335 Steigman July 24, 1934 2,110,193 Best Mar. 8, 1938 2,668,251 List Feb. 2, 1954 FOREIGN PATENTS 686,958 =France Apr. 22, 1930 336,491 Great Britain Oct. 16, 1930 385,290 Great Britain Mar. 19, 1931 

